Construction of stable niches for denitrifiers using 3D bioprinting for efficient nitrogen removal.

The denitrification process is the core of biological nitrogen removal technology, but its efficacy is limited by the fragile ecological niches of denitrifying bacteria. This study successfully created three-dimensional (3D) denitrification living materials by the controllable and biocompatible 3D bioprinting technology, enabling the construction of artificial 3D microscale structures that facilitate microenvironments for the efficient dynamic reactions of denitrifying bacteria. By developing the double network structure of sodium alginate-gelatin, the bioink with easy extrusion and robust mechanical properties was obtained. Subsequently, the denitrifying bacteria were arranged in three dimensions through a 3D bioprinting platform, and the living materials characterized by precisely controlled three-dimensional morphology and excellent dynamic metabolism were created. The results further indicated that the stable denitrifying bacterial niches were successfully established within 3D living materials, resulting in a significant improvement in the denitrification performance. Additionally, the 3D living materials still maintained high bacterial activity at the low temperatures, showing their potential for repeated use and tolerance to adverse conditions. This study demonstrated the potential of 3D bioprinting technology in constructing living materials with ideal bacterial niches for efficient wastewater treatment, thereby offering novel avenues for addressing the water pollution concerns.